Packaged RF power devices typically include a transistor die mounted on a base and enclosed in a package. An RF input signal is supplied to the transistor through an RF input lead that extends from outside the package to the inside of the package, and an RF output signal is delivered from the device through an RF output lead that extends from inside the package to the outside. An input matching circuit can be included within the package, and can be connected between the RF input lead and an input terminal of the RF transistor. The input matching circuit provides an impedance match at the input of the transistor at the fundamental operating frequency of the transistor. An output matching circuit can also be included within the package, and can be connected between an output terminal of the RF transistor and the RF output lead. The output matching circuit may provide an impedance match at the output of the transistor at the fundamental operating frequency of the transistor.
The RF transistor can include a large periphery transistor die that includes a number of discrete transistor cells on a common substrate that are electrically connected in parallel. Input matching can be particularly beneficial for such devices, as it can increase the usable bandwidth of the devices. Furthermore, the impedance values of elements of the input and/or output matching network must be carefully selected to avoid creating odd mode oscillations. Selection of the impedance values, including selection of appropriate inductances through bond wire lengths, can limit the topology of the matching network.
Packaged RF power devices have air-cavity and overmold configurations. In an air-cavity configuration, elements of the packaged RF power device such as the transistor die and/or components of a matching network may be disposed in an air cavity within the packaged RF power device. In an overmolded plastic (OMP) configuration, elements of the packaged RF power device may be encased in a polymer material that surrounds and is in contact with the devices and bond wires of the packaged RF power device.